A wiki is a website designed for collaboration. Unlike a traditional website where pages can only be read, in a wiki everyone can edit, update and append pages with new information and without knowing HTML.
Wikis are useful for many types of collaboration, from writing documents and managing projects to creating intranets or extranets.
Fixing errors on (or updating) most intranets can be cumbersome. A user must:                Document the problem        Figure out who has the power to make changes        Convince them to do it        Wait for that person to do the work        
Most people find it's not worth the trouble. The intranet withers slowly.